How Should Screw Conveyor Covers Be Fastened?

Question:

We are replacing worn covers on several screw conveyors at our plant, ranging from 6-inch to 24-inch diameter. Some of the existing covers are bolted, and some are clamped. How should the new covers be fastened, how far apart should the fasteners be, and does the spacing change with conveyor diameter?

Answer:

KWS recommends bolting all screw conveyor covers. The cover contains the bulk material and serves as a guard between personnel and the rotating screw. Bolts secure the cover firmly against the trough flange and cannot be removed by hand. Access to the rotating screw is eliminated.

Bolt spacing depends on your application and not on conveyor diameter. Screw conveyors in general applications are typically bolted on 24-inch centers. Screw conveyors that must contain dust, shed weather outdoors, or seal against slight pressure are bolted on 12-inch centers, and the most demanding applications require covers bolted on 6-inch centers. Bolts are placed on both sides of the cover, at each corner, and at every cover joint so the ends cannot lift. Gasket material is installed between the cover and the trough flange.

KWS provides two safety bolts per cover, staggered on opposite corners. Each safety bolt has a special head that requires a safety key for removal, which restricts cover access to only trained maintenance personnel. Assembled screw conveyors ship with safety bolts installed, and loose cover shipments include the safety bolts and safety key.

Screw clamps can be used in place of bolts at the customer’s discretion and must be installed and tightened with a wrench to provide sufficient clamping force. Recommended clamp spacing is the same as bolted covers. Two safety bolts per cover are still required. KWS reviews every application and recommends cover fastening that keeps material contained and personnel safe.